Music typewriters were developed in the 19th century, but it wasn't until the mid 1900's that they became popular. Musicians usually specialized in using these machines. Several different models were invented, but there were two different concepts that became standard. The Keaton Music Typewriter looked very different from a regular typewriter. It had two keyboards, one which was movable and one stationary. The other models were much like a regular typewriter. They employed musical symbols instead of letters. Staff paper or blank paper was slipped in the carriage and the keys struck. After the music was printed on a music typewriter, the original was photographed or copied to make the extra copies necessary to distribute and sell.